Like its predecessors, this Tinkertoy-compatible bearing system uses ten 4.5mm BB's to provide smoother rotation than the stock wheels included with a Tinkertoy set: (http://bit.ly/1ngex61)
The center bore is *just* a little loose on a Tinkertoy rod (not renowned for their precision diameters in the first place) so if you really need the bearing to stick fast I recommend using a little piece of painters' tape around the rod.
It's modeled in three parts for ease of assembly, but you'll need to super glue the two halves together.

Threeding.com is a marketplace for free and paid 3D printing models and files.
On our online platform individuals and businesses can buy, sell or just exchange freely 3D model suitable for 3D printing.